Abstract
Historically, impedance measurement has been applied to the study of metal corrosion, but a growing body of work is reporting its increasingly frequent use in the case of batteries, to study electrode performance before, during and after charging/discharging (behavioral, failure or aging studies).
In fact, impedance reflects the difficulty of current flowing through any electrical component. It is the generalization of the concept of resistance (which remains limited to the case of the perfect ohmic conductor) to all electrical components. In fact, many of these components (coils, capacitors, etc.) exhibit more complex behaviors when subjected to the passage of a current.
In most cases, batteries can be described as a juxtaposition of these different electrical components. In particular, the electrolyte can be modeled as a simple resistor, since it behaves essentially as an ohmic conductor. The kinetics of redox reactions, when a potential is applied to the electrodes, are fairly well described by a charge transfer resistance (Rtc). At the electrode/electrolyte interface, a double layer exists. This is formed when a front of ions from the electrolyte solution appears on the electrode surface. This ion plane and the electrode plane form the armatures of a very thin pseudo-capacitor (Cdc). The value of these last two parameters depends on many variables, such as temperature, the concentration of ions in solution, roughness, but also the adsorption of species or the formation of a film on the electrode surface. Electrode/electrolyte interfaces can change over time and/or during operation. Impedance monitoring is therefore the best way to model batteries (using more or less complex RLC circuits), to understand their intimate mechanisms and thus to propose solutions for optimizing their performance, depending on the constraints of use.
